Chapter 3
Innate Immunity
Dr. Capers
Kindt • Goldsby • Osborne
Kuby IMMUNOLOGY
Sixth Edition
Chapter 3
Innate Immunity
Copyright © 2007 by W. H. Freeman and Company

Vertebrate are protected by 2 systems of
immunity
○ Innate Immunity
○ Adaptive Immunity
- Takes time but has memory
Innate Immunity can be found in all
multicellular plants and animals
 Adaptive Immunity evolved in jawed
vertebrates

Innate Immunity

Innate Immune System:
 Physical Barriers
 Skin and mucous membranes
 Chemical Barriers
 Acidity of stomach, antimicrobial molecules
 Cellular Barriers
 Cells with sensitive receptors that can detect
microbial invaders
Innate Immunity

Antimicrobial Proteins
○ Psoriasin – produced by skin
- Antibacterial activity to E. coli
○ Help when skin is scratched or cut to prevent
infection
○ Saliva, tears, and mucous membranes help to
wash invaders away as well as contain
antimicrobial peptides
Innate Immunity

Normal flora
○ Help to out-compete pathogens for space and
nutrients

Connection between adaptive and
innate immunity
○ Pathogens may get past anatomical barriers
○ Interact with membrane-bound molecules
(sensors) that recognize broad structural
motifs of microbial species
- Pattern Recognition Receptors (PRRs)
- On pathogen it is called Pathogen-Associated
Molecular Patterns (PAMPs)

Pattern Recognition Receptors (PRRs)
○ In contrast, antibodies and T cell receptors
recognize finer details of molecular structure
○ If PAMPs are detected, complement system
will be activated

Complement System
○ One part is a collection of proteins that form
aggregates that punch holes in pathogen’s
cell membrane causing lysis
○ Include serum glycoproteins that promote
uptake of pathogens by phagocytes
(opsonization)
○ Complement system ties innate and adaptive
immunity

Dendritic cells and Macrophages have
variety of receptors
○ Toll-like receptors – detect microbial products

Activated macrophages will secrete
cytokines
○ Hormone or growth-like factors to induce
specific cell activities (upregulation of B and T
cells); again tying innate and adaptive
immunity
Inflammation

Hallmarks
○ Swelling
○ Redness
○ Heat
○ pain
Inflammation

Within minutes of tissue injury:
○ Vasodilation – rise of blood volume to area
○ Vascular permeability increases –
accumulation of fluid
- Edema
○ Leukocytes adhere to endothelial cells and
pass through walls of capillaries into tissues extravasation
Inflammation

Extravasation
 Inflammatory response develops – various
cytokines and inflammatory mediators act on
endothelium of blood vessels
 Increased expression of Cell Adhesion Molecules
(CAMs)
 Cells, such as neutrophils, adhere to endothelium
using these CAMs strongly enough not to be swept
away by flowing blood
 Then they must penetrate the wall of the vessel to
move into the tissue
Inflammation

Neutrophil Extravasation
○ Rolling
○ Activation of chemoattractant stimulus
○ Arrest and adhesion
○ Transendothelial migration into tissue
Antimicrobial Peptides
Isolated from humans, frogs, flies,
nematodes, plants
 Range from 6-59 amino acids long
 Good source in humans is the neutrophil
 Work by disrupting microbial membrane

○ How do they discriminate between microbial
and host membrane?
○ Big area of research
C Reactive Protein

Recognizes ligands on surface of
microbes
 Helps in phagocytosis
 Activates complement-mediated attack
Pattern Recognition Receptors – Toll-like
Receptors

1980s
 Toll in flies
○ Important in fly development

1996
 Toll in fruit flies
○ Mutation caused susceptibility to infection of
fungus

1997 (Janeway)
 Found that Toll-like receptor activated
expression of immune response genes
 Made of leucine-rich repeat sequences
Cell Types of Innate Immunity
Monocytes have many of the same functions
As macrophage
Signal Transduction Pathways

Signal

Microbial product

Receptor

Extracellular portion
of TLR

Interactions of intracellular
molecules – phosphorylation;
signal transduction pathway –
promotes phosphorylation of
transcription factors in nucleus

Cell differentiation,
inflammation, antigenpresentation, etc

Signal Transduction

Effector Mechanism
Adaptive Immunity tends to be found in
vertebrates
 However, do find innate immunity in
nonvertebrates, even plants

○ Sea squirt (chordate) – complement, TLRs
○ Fruit Fly – TLRs, antimicrobial proteins
○ Tomato – oxidative bursts, enzymes that
digest fungi, plant can isolate infection by
strengthening cell walls